The posted price of $175 is way too much, imo. On the other hand, $75 would not be so bad if for that you were getting, say, a CD bezel and other working parts to keep a machine going if need be, even with a dud logic board. But you could do better, too. $100-ish has been the typical asking price for one of these on the usual auction site in recent years…. They don’t sell especially well, though in fact they are great machines. A Quadra 650/800 is also a better bet, as they were faster and ethernet and fpu were standard in them. A 7100 board will also fit a P600 case, with some dremmel work.
As for the problem with the Centris, any machine that boots and freezes always sounds suspiciously to me like a machine without scsi ID and termination properly set up, or with a corrupt system, or some similar small problem like RAM needing reseated. Is the seller a vintage Mac enthusiast who knows what he/she is doing, especially when swapping disks into the machine? If not a vintage machead, the machine might just be worth a gamble at an attractive-enough price. Those boards are pretty reliable, and recapping is not typically necessary.
